The present study aims at analyzing the heat transfer and pressure drop characteristics the by determination of improved Nusselt number in a double pipe heat exchanger, whose outer surface of the inner tube is modified through the shot peening process. The attained convective heat transfer coefficient (CHIC) and pressure drop of water flow in the heat exchanger with this modified surface are first measured and compared with a high conductivity copper tube construction. The study is to analyze the variations in CHIC and the pressure drop of the activated carbon (AC) - solar glycol (SG) based nanofluid. The experiments stimulated nanomaterials volume concentrations of the nanofluids such as 0.2%, 0.4% and 0.6%. The Nusselt numbers at mass flow variation rates in the range of 0.04, 0.055 and 0.08 kg/sec with shot peened heat exchanger. The presence of AC nanomaterials in the SG enhances the Nusselt number by 26.25%, 40.79%, and 57.06% for 0.2, 0.4 and 0.6% volume concentrations respectively, at a mass flow rate of 0.04 kg/sec in the shot peened heat exchanger. The average CHIC of the nanofluid containing 0.6% of AC nanomaterials is noted to be augmented to a maximum of 71% at 0.04 kg/sec. (C) 2019 Published by Elsevier Ltd.